The subtitles are actually fairly accurate to the Cantonese dialogue, at least to what some of them suggest in Cantonese. (Like the "I'll stick it in my ass" comment, which was just insinuated in the Cantonese dialogue). And there are some additions, but then a lot of subtitles tend to do that too (Japanese is the worse because it's hard to translate polite speech into English because they don't really exist. There are always different translation in different movies of the same polite greeting.)
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My blog on Asian films - http://thegoldenrock.blogspot.com/
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"So one day we may find ways to get this Chinese guy some groove"